In order to prepare cells for transfusion or transplantation, it may be necessary to process the cells using an operation, which removes unwanted chemical and/or cellular elements. For example, in preparing frozen erythrocytes for transfusion, erythrocytes are separated from cryopreservatives and other blood components, such as white blood cells, platelets, and subcellular debris. It is important that cell processing be performed under conditions which minimize the risk of microbial contamination.
Further where cell (such as eukaryotic cells, bacteria, or yeast) are cultured in bioreactors for the synthesis of pharmaceuticals, it is necessary to separate the cells from their culture medium.
A number of devices and techniques have been developed to process cells for the foregoing purposes, as described, for example, in European Patent No. 00575858/EP B1 by Witthaus et al. And U.S. Pat. No. 4,919,817 by Schoendorfer and Williamson, and other patents as set forth below.
Generally, cell processing requires steps in which cells or cell elements are separate from a liquid phase. This separation is typically accomplished by centrifugation.
Also as part of the separation process, a number of devices have been developed which incorporate a means of expressing (i.e., promoting the exit) fluid which has been removed from harvested cells. Disclosures relating to expression include U.S. Pat. No. 4,332,351 by Kellogg and Druger, U.S. Pat. No. 4,010,894 by Kellogg and Kruger, U.S. Pat. No. 4,007,871 by Jones and Kellogg, U.S. Pat. No. 3,737,097 by Jones et al., EP 00265795/EP B1 by Polaschegg, U.S. Pat. No. 4,934,995 by Cullis, U.S. Pat. No. 4,223,672 by Terman et al., and U.S. Pat. No. 4,213,561 by Bayham.
The present invention relates to biological fluid and/or cell processing apparatus and, more particularly, to an apparatus for separating fluid materials having different densities from each other, most typically in a centrifugal field, or otherwise such as in a gravitational field. More particularly, the present invention relates to an apparatus designed to add additional fluids to wash or otherwise treat one or more of the cellular components after the less dense fractions of the solution have been separated and expressed from, or pushed out of, the centrifugal (or gravitational) field. Automated systems for processing cellular material in this manner have typically relied on inefficient centrifugal containment devices and complex fluid management hardware to remove the separated fractions from the centrifuge chamber. Sterility, temperature control, ratio of volume of input fluids, ability to process variable volumes and simplification of the mechanisms used for expressing materials out of a cell or fluid processing chamber are concerns that have been addressed in a variety of inefficient or expensive apparatus and methods in the past.